mechanical and electrical problems can be taken care of fairly easily. rust is your worst enemy.
thoroughly check the heater channels, pans (especially under the battery under the back seat), rear crossmember, lower inner front firewall and under the pedal cluster, bumper to body mounts front & back, lower fender wells on all corners (especially at the back near the end of the heater channel) and lower rear 1/4 panels.
check the front & rear aprons for damage due to a collision.
as for price, it really depends on the overall condition of the car. could be $500 or $5000.
supers are good cars. they handle well and drive well if the engine is tuned right.
good luck.